In Port Mercy, Alaska, everyone trusts Cole Mercer.He teaches teenagers how to repair marine engines, survive dangerous water, and recognize trouble before it becomes disaster. His first rule is simple: nothing moves until everyone knows how to stop it.Then a cruise passenger disappears.Seventeen-year-old Tessa Ward begins noticing things that don't fit: a missing tool in Cole's meticulously ordered shop, unsettling questions from police around the harbor, and moments when her admired instructor's calm precision feels less reassuring than calculated.Cole has taught his students that machines don't lie. Every failure has a cause. Every missing part leaves a question. And every system has a point where one deliberate interruption can stop it completely.As Tessa follows the evidence hidden inside the lessons Cole taught her, she begins to understand that knowing how something works may be the only way to survive the person who built the system.Set against the rain-dark harbors and unforgiving waters of coastal Alaska, KILL SWITCH is a tense psychological crime thriller about trust, manipulation, courage, and the moment when knowing how to stop something matters more than knowing how to make it run.